The present invention'disclosed herein relates to a touch screen, and more particularly, to a device and a method for compensating sensing capacitance variations of a touch panel and compensating offset variations of a charge amplifier in an input unit of a controller in order to reduce sensing errors.
A touch screen is one of the most popular human-machine interfaces. The touch screen is used for a variety of applications such as Automated Teller Machines (ATMs), laptop Personal Computers (PCs), and mobile devices. The touch screen may execute different functions easier by touching or moving a cursor on a screen without external input devices such as keyboard and a mouse. Due to these characteristics, the touch screen is recognized as more effective interface in terms of convenience, flexibility, and cost, compared to a keyboard, a mouse, or a key panel exclusive solution.
A touch event of the touch screen may be sensed through various methods. For example, a touch event of the touch screen may be sensed through resistive, infrared, infrared image, surface acoustic wave (SAW), acoustic pulse recognition (APR), and capacitive sensing methods.
Among them, the capacitive sensing method may be classified into a projected sensing method and a surface capacitive sensing method. The projected capacitive sensing method receives great attentions because it may recognize multi-touch events.
However, the projected capacitive sensing method may cause sensing errors because of sensing capacitance variations of a touch panel and offset variations of a charge amplifier in an input unit of a controller. The sensing capacitance variations, and offset variations of the input unit of the controller may originate from manufacturing process variations of sensing capacitors. Therefore, in order to reduce sensing errors and accurately sensing a touch event on a touch screen, solutions for compensating the sensing capacitance variations and the offset variations are required.